For the 1991 ACTG recompetition, the independent ACTUs at Cornell University Medica College (CUMC) and Memorial Sloan-Kettering Cancer Center (MSKCC) have elected to merge as one Main ACTU and add two new Subunits, St. Clare's Hospital in Manhattan and North Shore University Hospital on Long Island. MSKCC is also applying for Virology and Pharmacology Core Laboratories. The merger of the CUMC and MSKCC ACTUs will provide the key opportunities to (a) streamline and consolidate shared ACTU activities, (b) increase cost efficiency while maintaining enrollment, and (c) rationally focus and direct high priority trials at one site which has either recognized clinical expertise or an optimal dedicated clinical facility. The addition of St. Clare's (the most active HIV Unit on the East Coast) and North Shore as Subunits will enhance accrual of women, minorities, IVDUs, and prisoners, extend the ACTG network to underserved areas of New York City (Queens) and Long Island, and provide the ACTG with additional investigators expert in HIV-related disease. The CUMC and MSKCC ACTUs have made clear scientific contributions to the ACTG, and have demonstrated high-level accomplishments in phase I, II, and III protocols in three ACTG priority areas: Primary HIV Infection, Opportunistic Infections (OI), and Oncology in OI trials enrollment, CUMC- MSKCC together ranks first in New York City and seventh nationally, and in Oncology trials enrollment ranks first in New York City and second nationally. Maintaining this high level of participation in OI and Oncology studies will be the primary objective of the new CUMC-MSKCC ACTU and its Subunits. In addition to the large endogenous patient populations already at the Main CUMC-MSKCC ACTU sites and the two Subunits (both are New York State Designated AIDS Care Units), more than 40 separate linkages will also be used as sources of trials patients with clear emphasis on recruitment of under-represented groups. Other particularly important components of the new CUMC-MSKCC ACTU include a new large (dedicated) outpatient unit, a supportive GCRC, investigators skilled in OI and Oncology trials, an active Community Advisory Board, and nursing, administrative, data management, and pharmacy staffs thoroughly experienced in ACTG clinical trials work. Together, CUMC-MSKCC with its Subunits provides a unique ACTU for conducting high priority ACTG studies.